Hello Robert,
Whilst I agree that the mechanics of undoing and remaking a gas connection are not complex, what is often overlooked by casual fitter is the legal requirement for the gas soundness of the system to be proven.
Most casual fitters do not have access to the equipment to complete this required element, and even if they have the equipment, they may not know the process and criteria and standards that have to be applied.
Failure to complete the tests is by definition incompetence, and that is a breach of health & safety law, which is a criminal offence.
We must not forget that it is not just the gas fitting that must be compliant, it is the whole function of the gas appliance.
I have seen the aftermath of gas fitting work that was not compliant, and the damage to lives that can be caused is very distressing.